CHARACTERIZATION OF PWR CRUD PHASES AND THEIR VARIATION UNDER PLANT OPERATION BY TRANSMISSION ELECTRON MICROSCOPY

摘要

The solid particles suspended and circulated in PWR primary water may consist of fuel CRUD, solid corrosion products of water-contacting materials, additives and various impurities of reactor water. This paper demonstrates a new methodology by using transmission electron microscopy to characterize the phase compositions of CRUD particles and their variation under reactor operation. Several new CRUD phases have been imaged and confirmed by energy dispersive X-ray spectroscopy and selected area electron diffraction studies. The differences in CRUD phase composition between scraped fuel CRUD, CRUD from primary water in an event of elevated Co-58 activity or shutdown or H_2O_2 injection are reported and discussed with respect to the thermodynamic stability of some phases and possible chemical reactions involved.